Recovery of wool from wool-acetate fabrics



Patented June 7, 1949 UNITED STATES RECOVERY OF WOOL FROM WOOL-ACETATEFABRICS George C. Ward,

Genazzani, New York,

Cumberland, Md., and Roger U.

N. Y., assignors to Celanese Corporation of America, a corporation ofDelaware No Drawing. Application March 10, 1944, Serial No. 525,954

6 Claims.

This invention relates to the treatment of mixed textile materials andrelates more particularly to the treatment of textile materialscomprising a mixture of wool and organic ester of cellulose fibers,whereby the wool fibers may be recovered in an economical and convenientmanner.

An object of this invention is the provision of a novel process for therecovery of wool fibers from textile materials comprising wool andorganic ester of cellulose fibers.

Another object of this invention is the treatment of waste materialscomprising wool and organic ester of cellulose fibers whereby theorganic ester of cellulose fibers may be removed and clean, strong woolfibers of unimpaired textile properties may be recovered.

Other objects of this invention will appear hereinafter from thefollowing detailed description.

In textile operation-s involving the use of wool and cellulose acetateor other organic ester of cellulose yarns, there isproduced a certainproportion of waste consisting of a mixture of wool and celluloseacetate or other organic ester of cellulose fibers. Such mixtures may bedyed in a solid shade, but the dyed mixture is of value only where thereis a need for a textile material containing the particular fibers in theprecise proportions present in the waste. Where, for example, a mixtureof wool and cellulose acetate fibers is available and only therelatively valuable wool in the mixture is desired the only practicalsolution to the recovery of the wool is to remove the non-woolenmaterials. The recovery of the wool must, of course, be effected in sucha manner that the wool fibers are left undamaged. Such a process,adapted to commercial operation, has long been sought.

We have now discovered that mixtures of textile materials comprisingwool and cellulose acetate fibers may be treated in a novel manner andpure Wool fibers of unimpaired textile properties may be recoveredtherefrom. In accordance with our novel process, this valuable resultmay be achieved if a mixture of waste fibers comprising wool andcellulose acetate fibers, from which the color is preferablysubstantially stripped, is subjected to the action of an alkalinesaponification bath of a particular composition and concentration,whereby the cellulose acetate fibers are saponified to yield regeneratedcellulose fibers and, following saponification, the resulting mixtur issubjected to carbonization whereby the cellulosic fibers are removed.The carbonization treatment eliminates the cellulosic fibers present andthe product recovered comprises clean wool fibers free of all non-woolenmaterials and possessing eminently satisfactory textile properties.

The saponification of the cellulose acetate fibers in the mixturewithout injury to the wool fibers present requires careful control ofboth the temperature and composition of the saponifying bath, since woolfibers, as is well known, are quite sensitive to the action of alkalinematerials. We have found, however, that the disadvantageous effects ofalkaline media on wool may be overcome by incorporating in thesaponifying bath an inorganic salt which acts to inhibit the action ofthe alkali on the wool. Asexamples of suitable salts, there may bementioned sodium sulfate, sodium chloride or sodium acetate. Suchinhibitors may comprise from 5 to 25% by weight of the saponifying bath.As suitable saponifying agents, we may employ inorganic agents such as,for example, sodium hydroxide, potassium hydroxide, sodium silicate,ammonium hydroxide and sodium carbonate, or organic agents such as, forexample, methyl amine, ethylene diamine, triethanolamine, or otherorganic bases. The saponifying baths employed are preferably aqueoussolutions containing the saponifying agent in a concentration of 0.1 to

1%. Satisfactory results are achieved with the saponifying bath attemperatures of 10 to 50 C. and the saponification may be continued for20 minutes to 24 hours. The most advantageous results are obtainedemploying an aqueous saponifying bath comprising about 0.2 to 0.6% byweight of sodium hydroxide containing 15 to 20% of sodium sulfate andsaponifying for 30 minutes to 16 hours at 20 to 40 C. The more dilutethe solution employed the more extended may be the period ofsaponification.

The carbonization may be effected by treating the mixture of wool andcellulosic fibers with a solution of a suitable carbonizing agent at atemperature of about 15 to 40 0., say room temperature, removing thefibers from the solution, drying, and then baking for 5 to 30 minutes ata temperature of to C. After baking, the dry fibers are shaken in aduster, neutralized, if desired, rinsed well and dried. The wool fibersobtained after carbonization may be utilized in any application Wherewool fibers are normally employed and retain all of their desirabletextile characteristics.

As suitable carbonizing agents we may, for example, employ'aqueoussolutions of sulfuric acid or aluminum chloride, which agents may bepresent in solution in concentrations of from 4 to 8%. Optimum resultsare achieved employing the carbonizing agent in concentrations of 2 to7%. Gaseous hydrogen chloride may also be employed as the carbonizingagent in place of aluminum chloride which, of course, yields hydrogenchloride when heated during the baking operation.

Although we have indicated in the foregoing detailed description thatthe recovered wool fibers are free of cellulose ester materials afterbeing processed in accordance with our invention, it is to beunderstood, however, that in large scale commercial operations someincompletely saponified cellulose ester fibers may remain afterprocessing, especially where some of the cellulose ester fibersoriginally present in the mixture are of relatively high denier. Thesaponification need not be efi'ected, usually, under such conditions asto make complete saponification of such heavy denier fibers absolutelycertain. The presence of such incompletely saponified fibers in anamount of 1 to 2% by weight, or even more, in some instances, may becompletely disregarded from a practical point of view since such amountcannot be detected in the wool fibers by visual examination even whensamples of the recovered wool fibers are dyed with dyestuffs having anaifinity for wool only and the wool is dyed in deep shades.

While our invention has been described more particularly in connectionwith the treatment of waste materials comprising wool and celluloseacetate materials to recover the wool fibers therefrom, mixtures ofwool, cellulose acetate and cellulosic fibers are commonly encounteredin commercial operations and the examples will be directed to therecovery of wool fibers from such mixtures.

In order further to illustrate our invention but without being limitedthereto the following examples are given.

Example] 200 parts by weight of a mixture of colored waste staple fiberscomprising 60% by weight of wool fibers, 6% by weight of celluloseacetate fibers, 24% by weight of cellulose fibers and 10% of oil arestripped of theircolor by treating for 20 minutes in a 1% solution ofsodium hydrosulphite at 50 C. and are then rinsed well in warm water.This treatment does not remove the color entirely but lightens theover-all color effect to a substantial degree. The stripped mixture ofwaste fibers is then immersed in a saponifying bath comprising 0.6% byweight of sodium hydroxide and 20%. of sodium sulfate at a temperatureof 40 C. for 30 minutes. The fibers are removed, rinsed well and thencarbonized by immersion in a 6% aqueous solution of sulfuric acid at 28C. for 10 minutes. The fibers are removed, from the sulfuric acidsolution, dried and then baked at 100 C. for 10 minutes. The driedfibers are rinsed again after baking, and after drying, the fibersremaining after this treatment are found to be substantially free of allcellulose acetate and cellulosic fibers and to comprise pure woolfibers. The wool obtained is of unimpaired textile properties.

Example II In lieu of employing asaponification process as given above,the stripped mixture of waste fibers may be saponified in a solutioncomprising 0.2% of sodium hydroxide containing by weight of sodiumsulfate at 20 C. for 16 hours. After being rinsed well, the treatedfibers may be carbonized by treatment with a 7% aqueous solution ofaluminum chloride at 28 C. for 10 minutes, dried, and baked at C. for 10minutes. The dry fibers are dusted, rinsed in a 1% solution ofhydrochloric acid, which is followed by a second rinse in warm water.After drying, the fibers are found to be substantially free of anycellulose acetate and cellulosic fibers and may be spun into woolen orworsted yarns whose textile properties are entirely satisfactory.

It is to be understood, of course, that our novel process may be appliedto any textile material, such as, for example, a fabric made of orcontaining a mixture of textile fibers comprising wool and celluloseacetate or wool, cellulose acetate and cellulosic fibers, and aftertreatment a pure Woolen fabric may be obtained. In this manner, manynovel and decorative effects may be obtained by weaving a fabric of wooland cellulose acetate yarns or fibers and then removing all of thenon-woolen fibers.

While the foregoing description is directed primarily to the treatmentof mixtures of wool with cellulose acetate, which mixture may containcellulosic fibers, other organic esters of cellulose such as, forexample, cellulose propionate, cellulose butyrate and celluloseacetate-butyrate, may be removed in like manner from textile materialsin which they are present together With wool.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by LettersPatent is:

Process for the recovery of wool from mixed textile materials containingwool and cellulose acetate fibers, which comprises immersing said fibermixture in an aqueous solution containing from 0.1 to 1% of sodiumhydroxide and 5 to 25% of sodium sulfate so as to cause thesaponification of the cellulose acetate fibers to yield regeneratedcellulose, and carbonizing the cellulose fibers from the fiber mixture,whereby wool fibers substantially free of other textile materials areobtained.

2. Process for the recovery of wool fibers from mixed textile materialscontaining wool and cellulose acetate fibers, which comprises im mersingsaid fiber mixture in an aqueous solution containing from 0.1 to 1% ofsodium hydroxide and 5 to 25% of sodium sulfate so as to cause thesaponification of the cellulose acetate fibers to yield regeneratedcellulose by maintaining the fiber mixture in said aqueous solution forfrom 20 minutes to 24 hours at 10 to 50 C., and carbonizing thecellulose fibers from the fiber mixture, whereby wool fiberssubstantially free of other textile materials are obtained.

3. Process for the recovery of wool fibers from mixed textile fiberscontaining wool and cellulose acetate fibers, which comprises immersingsaid fiber mixture in an aqueous solution containing 0.6% of sodiumhydroxide and 20% of sodium sulfate for 30 minutes at 40 C. to cause thesaponification of the cellulose acetate fibers and to yield regeneratedcellulose, and then carbonizing the cellulose fibers from the fibermixture, whereby wool fibers substantially free of other textilematerials are obtained.

4. Process for the recovery of Wool fibers from mixed textilefiberscontaining wool and cellulose acetate fibers, which comprisesimmersing said fiber mixture in an aqueous solution containing 0.2% ofsodium hydroxide and of sodium sulfate for 16 hours at 20 C. to causethe saponification of the cellulose acetate fibers and to yieldregenerated cellulose, and then carbonizing the cellulose fibers fromthe fiber mixture, whereby wool fibers substantially free of othertextile materials are obtained.

5. Process for the recovery of wool fibers from mixed textile fiberscontaining wool and cellulose acetate fibers, which comprises immersingsaid fiber mixture in an aqueous solution containing 0.6% of sodiumhydroxide and 20% of sodium sulfate for minutes at C. to cause thesaponification of the cellulose acetate fibers and to yield regeneratedcellulose, rinsing the fiber mixture, and then carbonizing the cellulosefibers from the fiber mixture by immersing the fibers in 6% aqueoussulfuric acid at 28 C. for 10 minutes, drying, baking the fibers at C.for 10 minutes, dusting, neutralizing, and rinsing, whereby wool fiberssubstantially free of other textile materials are obtained.

6. Process for the recovery of wool fibers from mixed textile fiberscontaining wool and cellulose acetate fibers, which comprises immersingsaid fiber mixture in an aqueous solution containing REFERENCES CITEDThe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,804,529 Dreyfus May 12, 19311,980,191 Dickie Nov. 13, 1934 2,002,083 Dreyfus May 21, 1935 2,152,640Ferguson Apr. 4, 1939 OTHER REFERENCES Mercerising Wool Mixtures-page ofthe Textile Manufacturer for April, 1943.

